Based on
http://www.codinghorror.com/blog/2012/10/the-future-of-markdown.html a
post by Jeff Atwood, where he introduces his ideas for standardizing
Markdown for the future.

Quote I don’t want to extend Markdown by adding tons of crazy new
functionality, or radically change the way it currently works, or
anything like that. I’d be opposed to such changes. I just want to
solidify and standardize the simple, useful version of Markdown that
is working so well for everyone right now. I want there to be an
unambiguous, basic standard that everyone using Markdown can expect to
work in the same way across all web sites in the world when they begin
typing.

Talking to Ian at W3C it seems that Google Chrome and IE9 have issues when editing Community pages. On Chrome I overcame this by allowing Chrome to load the page by selecting the small ‘shield’ shape at the right hand end of the address bar. This allows the group member to edit the text of pages.
It is currently being investigated by W3c